Polar aprotic solvents such as cyclic or linear carbonates, or ethers used alone or in mixtures, are known in various electrolytic compositions. The stability of these products towards highly negative potentials, close to those of alkaline metals, or highly positive (≧4V with respect to Li+/Lio), are not satisfactory, and lithium batteries containing electrolytes obtained from the dissolution of a lithium salt in these solvents create serious safety problems. Products of the amide type, whether linear or cyclic, such as dimethylformamide or N-methylpyrrolidinone, possess excellent properties as solvents, but are oxidized at potentials that are still lower, in the order of 3.7 V with respect to Li+/Lio.
Numerous materials of positive electrodes, such as mixed oxides of transition metals and lithium work under potentials near 4 V with respect to Li+/Lio and therefore require electrolyte stabilities significantly higher than that value. For example, products like Li1−yCo1−x−zNixAlyO2 wherein x+y≦1 and z≦0.3); manganese spinels Li1−αMn2−xMxO4.Li1−αCo1−x−yNixAly wherein 0≦x+y≦1; 0≦y≦0.3; 0≦α≦1 and M=Li, Mg, Al, Cr, Ni, Co, Cu, Ni, Fe.
U.S. Pat. Nos. 4,851,307 and 5,063,124 describe electrolytes comprising a salt, a solvating polymer and an aprotic sulfamide of the general formulaR1R2NSO2R3R4 wherein R1, R2, R3 and R4, the same or different, are independently selected from C1-10alkyl or C1-10oxaalkyl. An example of the product of that group is the tetraethylfulfamide (R1═R2═R3═R4═C2H5). These materials have increased stability towards reducing or basic agents present and having potentials near those of alkaline metals. However, they are oxidized at potentials between 3.8 and 4V with respect to Li+/Lio.
EP 0 339 284 discloses dielectric and insulating compounds like perfluoro-acylamides or perfluoro-sulfonamides RFCONA1A2 and RFSO2NA1A2, wherein A1 and A2 are alkyl groups. The proposed use of these products in capacitors implies that the materials are not conductive and that the impurities and inevitable contaminants, particularly ionic products, are not inducing significant conductivity.
The publication of Sartori et al. in an abstract of a meeting of the Electrochemical Society, Volume 97-1, May 1997, describes certain sulfonamides that could be used as electrolytes in a battery or in an energy storage system.